CVE-2026-76910: Unleash Clone-feature Lets A User Copy Vulnerability

MODERATE
Advisory Identifier: GHSA-8xcj-9hfr-fh9j
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CWE-639
Published
Advisory Summary

CVE-2026-76910 is a MODERATE clone-feature lets a user copy vulnerability (CWE-639: Authorization Bypass Through User-Controlled Key) affecting Unleash libraries in the npm ecosystem. The issue involves clone-feature lets a user copy a feature from a project they cannot read. Remediation is available by upgrading affected packages to version 8.0.3.

CVE-2026-76910 at a Glance

CVE Identifier CVE-2026-76910
GHSA Identifier GHSA-8xcj-9hfr-fh9j
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-639: Authorization Bypass Through User-Controlled Key
Affected Product Unleash
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-76910

To remediate this vulnerability, upgrade all affected Unleash dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

unleash-server fixed: 8.0.3 
npm install unleash-server@8.0.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls unleash-server

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-76910, inspect your project dependencies using npm:

npm ls unleash-server

Analyze the terminal output to locate any version of Unleash in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 8.0.3), your application is affected.

Note: The npm ls unleash-server command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-639: Authorization Bypass Through User-Controlled Key, where the system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. In Unleash, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary The clone-feature endpoint supports copying features across projects, but it does not verify that the caller can access the source project. A user with _create_ permissions in one project can clone a feature from another project they cannot read and then inspect the copied configuration. This vulnerability cannot be confirmed without Enterprise access. Report is based on a circumstantial evidence in the open-source repository. ### Details `src/lib/features/feature-toggle/feature-toggle-service.ts` implements `cloneFeatureToggle`. This operation needs authorization for both sides: permission to read/copy the source feature and permission to create the destination feature. The clone path validates permissions against the destination project, but not against the source project that owns `featureName`. Because feature names are globally unique, a caller can reference a feature outside projects they can access. ### PoC 1. Create or identify two projects: `P1` with a private or restricted feature named `secret-feature`, and `P2` where the attacker has clone/create permissions. 2. Authenticate as the attacker. 3. Send: ```http POST /api/admin/projects/P2/features/secret-feature/clone Content-Type: application/json { "name": "secret-feature-copy" } ``` 4. Open `P2` and inspect `secret-feature-copy`. Verify if strategy parameters, constraints, variants, and variant payloads from the source feature have been copied. ### Impact Users with permissions on one project can disclose feature configuration from another project if they know or guess the source feature name. Feature names could be available in more public applications that have a common SDK access to multiple projects.

CVE-2026-76910 Affected Unleash Versions

1 component(s)
Fixed Versions:
8.0.3
Product / Package Ecosystem Affected Versions Fixed Version
unleash-server
npm/unleash-server
npm
< 8.0.3
8.0.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/Unleash/unleash/security/advisories/GHSA-8xcj-9hfr-fh9j
Security Fix Commit FIX COMMIT
https://github.com/Unleash/unleash/commit/2dc6ac0e8ba524ec7a2e9bc96a0e01d9d6f5a35a
Unleash Source Repository REPOSITORY
https://github.com/Unleash/unleash
Unleash Release RELEASE
https://github.com/Unleash/unleash/releases/tag/v8.0.3

Frequently Asked Questions

What is CVE-2026-76910?
CVE-2026-76910 is a security vulnerability in Unleash involving Clone-feature lets a user copy a feature from a project they cannot read under CWE-639: Authorization Bypass Through User-Controlled Key.
Which Unleash versions are affected?
Affected versions include releases prior to 8.0.3 across affected packages: unleash-server.
What version fixes CVE-2026-76910?
Upgrading to 8.0.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is unleash-server affected?
Yes, unleash-server is affected in releases prior to 8.0.3. Upgrade your dependency to 8.0.3 or later.
What CWE is associated with CVE-2026-76910?
CVE-2026-76910 is classified under CWE-639: Authorization Bypass Through User-Controlled Key (The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.).
How can I check npm dependencies for CVE-2026-76910?
Run the dependency tree command: 'npm ls unleash-server'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-8xcj-9hfr-fh9j",
  "modified" : "2026-09-22T20:34:40Z",
  "published" : "2026-09-22T20:34:40Z",
  "aliases" : [ "CVE-2026-76910" ],
  "summary" : "Unleash: Clone-feature lets a user copy a feature from a project they cannot read",
  "details" : "### Summary\n\nThe clone-feature endpoint supports copying features across projects, but it does not verify that the caller can access the source project. A user with _create_ permissions in one project can clone a feature from another project they cannot read and then inspect the copied configuration.\n\nThis vulnerability cannot be confirmed without Enterprise access. Report is based on a circumstantial evidence in the open-source repository.\n\n### Details\n`src/lib/features/feature-toggle/feature-toggle-service.ts` implements `cloneFeatureToggle`. This operation needs authorization for both sides: permission to read/copy the source feature and permission to create the destination feature.\n\nThe clone path validates permissions against the destination project, but not against the source project that owns `featureName`. Because feature names are globally unique, a caller can reference a feature outside projects they can access.\n\n### PoC\n1. Create or identify two projects: `P1` with a private or restricted feature named `secret-feature`, and `P2` where the attacker has clone/create permissions.\n2. Authenticate as the attacker.\n3. Send:\n\n```http\nPOST /api/admin/projects/P2/features/secret-feature/clone\nContent-Type: application/json\n\n{ \"name\": \"secret-feature-copy\" }\n```\n\n4. Open `P2` and inspect `secret-feature-copy`. Verify if strategy parameters, constraints, variants, and variant payloads from the source feature have been copied.\n\n### Impact\nUsers with permissions on one project can disclose feature configuration from another project if they know or guess the source feature name. Feature names could be available in more public applications that have a common SDK access to multiple projects.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
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      "name" : "unleash-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
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      }, {
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
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  }, {
    "type" : "WEB",
    "url" : "https://github.com/Unleash/unleash/commit/2dc6ac0e8ba524ec7a2e9bc96a0e01d9d6f5a35a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/Unleash/unleash"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Unleash/unleash/releases/tag/v8.0.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-639" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-22T20:34:40Z",
    "nvd_published_at" : null
  }
}